Class 8 Reproduction in Animals

1. Class 8 - Chapter 12
Reproduction in Animals

2. What are we going to study in this chapter:
1. Introduction - Definition and Modes of Reproduction
2. Sexual Reproduction
a. Male Reproductive Organs
b. Female Reproductive Organs
1. Fertilisation
a. Internal and External Fertilization.
b. Test tube baby
1. Development of Embryo
a. Viviparous and Oviparous Animals.
b. Young Ones to Adults
1. Asexual Reproduction
a. Binary Fission in Amoeba

3. Reproduction:
The process of giving birth to offspring or new one of its own kind is called Reproduction.
Reproduction is essential for the continuation of a species. Its ensures continuation of similar kinds
of individuals, generation after generation.
Organisms differ from one another but all are made up of cells.
Modes of Reproduction:
1. Sexual Reproduction :- The type of reproduction beginning from fusion of male and female
gameetes. The production of new living organisms by combining genetic information from two
individuals of different types.
1. Asexual Reproduction :- The type of reproduction in which only a single parent is involved is
called Asexual reproduction.

4. Male Reproductive Organs:
● It consists of testis, sperm duct and penis.
● Testis are involved in the production of male gametes
called Sperms. Sperm is a single cell.
● Millions of sperms are produced by the testis.
● Each sperm consists of three parts: Head, Middle piece
and Tail.

5. Female Reproductive Organs:
● It consists of ovaries, oviduct and uterus.
● Ovaries produce female gametes called Ova (eggs).
● A single matured egg is released from ovary into
oviduct every month.
● Baby develop in Uterus.
● Like Sperm, egg is also a single cell.

6. Fertilization:
● The first step in the process of reproduction is the fusion of a sperm and an ovum.
● When sperms come in contact with an egg, one of the sperms may fuse with the egg.
Such fusion of the egg and the sperm is called fertilization.
● During fertilization, the nuclei of the sperm and the egg fuse to form a single nucleus. This
results in the formation of a fertilized egg or zygote.
● The process of fertilization is the meeting of an egg cell from the mother and a sperm cell
from the father. So, the new individual inherits some characteristics from both parents.

7. Types of Fertilization:
1. Internal fertilization :- Fertilization which takes place inside the female body is called
internal fertilization. Internal fertilization occurs in many animals including humans, cows,
dogs and hens.
1. External fertilization :- Fertilization which takes place outside the female body is called
external fertilization. External fertilization is common in aquatic animals such as fish, starfish
etc.
Test Tube Baby:
Some women are unable to bear babies because sperms cannot reach the egg for fertilization. In
such cases, doctors collect freshly released egg and sperms and keep them together for a few
hours for IVF or in vitro fertilization (fertilization outside the body).
In case fertilization occurs, the zygote is allowed to develop for about a week and then it is placed
in the mother’s uterus. Complete development takes place in the uterus and the baby is born like
any other baby. Babies born through this technique are called test-tube babies. This term is
actually misleading because babies cannot grow in test tubes.

8. Development of Embryo: Fertilization results in the formation of zygote which begins to
develop into an embryo. The zygote divides repeatedly to give rise to a ball of cells. The cells then
begin to form groups that develop into different tissues and organs of the body. This developing
structure is termed an embryo. The embryo gets embedded in the wall of the uterus for further
development.The embryo continues to develop in the uterus. It gradually develops the body parts
like hands,legs etc. The stage of the embryo in which all the body parts can be identified is called a
foetus. When the development of the foetus is complete, the mother gives birth to the baby.

9. Viviparous Animals: The animals which give birth to young ones are called viviparous animals.
Oviparous Animals: The animals lay eggs which later develop into young ones are called oviparous animals.
Young Ones to Adults:
The new individuals which are born or hatched from the eggs continue to grow till they become adults. In some animals,
the young ones may look very different from the adults. Ex: life cycle of the silkworm (egg → larva or caterpillar → pupa →
adult) anf Frog is another such example (egg → tadpole (larva) → adult). The transformation of the larva into an adult
through drastic changes is called metamorphosis .

10. Asexual Reproduction:
Type of reproduction in which only a single
parent is involved is called asexual reproduction.
Since new individuals develop from the buds in
hydra, this type of asexual reproduction is called
budding.
Also, binary fission in Amoeba is example of
asexual reproduction.

12. Thank You ! Questions ?